1. Field of the Invention
The present invention relates to improvements in a clutch weight for use in a wet centrifugal clutch, and a process for producing the same.
2. Description of the Related Art
A clutch weight comprising a weight member made of a metal material, and a friction material bonded to the weight member is already known, for example, from Japanese Patent Application Laid-open No.11-125276. It is common that a friction material is bonded to a weight member formed by laminating and welding a plurality of iron plates one on another.
However, in the clutch weight including the weight member formed by laminating and welding the plurality of iron plates to one another, as described above, there is a possibility that a misalignment might be produced between the iron plates, resulting in an unstabilized clutch performance and in an injured appearance. To eliminate the misalignment between the iron plates, it is necessary to carry out a welding operation of a high accuracy, thereby bringing about an increase in cost. Further, when the characteristics required in the wet centrifugal clutch are changed, the number and shape of the iron plates in the conventional clutch weight must be set in accordance with the change in clutch characteristics, resulting in an increase in design load. This also brings about an increase in cost.
Accordingly, it is an object of the present invention to provide a clutch weight for a wet centrifugal clutch and a process for producing the same, wherein the cost can be reduced, while stabilizing the clutch performance and enhancing the appearance.
To achieve the above object, according to a first aspect and feature of the present invention, there is provided a clutch weight for a wet centrifugal clutch, comprising a weight member made of a metal material, and a friction material bonded to the weight member and capable of being brought into friction engagement with an inner periphery of a clutch outer, wherein the weight member is formed of a sintered alloy.
With such feature, a problem encountered in the conventional clutch weight including the weight member formed by laminating and welding the plurality of iron plates due to the misalignment between the iron plates can be eliminated by forming the weight member of the sintered alloy, thereby stabilizing the clutch performance and enhancing the appearance. Moreover, it is easy to change the density of the sintered alloy, and the clutch characteristics are also changed in accordance with the change in density. Therefore, it is possible to easily accommodate the change in characteristics required in the wet centrifugal clutch, thereby contributing a reduction in cost by cooperation with no need for a welding treatment.
According to a second aspect and feature of the present invention, in addition to the first feature, the weight member made of the iron-based sintered alloy has a density set at a value of 6 g/cm3 or more. With such feature, it is possible to provide a strength of the weight member equivalent to that of the conventional weight member formed by laminating and welding the plurality of iron plates one on another.
According to a third aspect and feature of the present invention, there is provided a process for producing a clutch weight for a wet centrifugal clutch according to the first or second feature, wherein the weight member resulting from the sintering of a sintering material is subjected to a steam treatment. According to such producing process, rusts are produced in the sintering material by contact of the sintering material with steam, whereby voids created in the weight member during the sintering can be eliminated to prevent the weight member from absorbing a lubricating oil as much as possible, leading to an enhanced oil resistance of the clutch weight.
The above and other objects, features and advantages of the invention will become apparent from the following description of the preferred embodiment taken in conjunction with the accompanying drawings.